Psicose (Allulose): properties, uses, pros, cons, safety

Psicose (d-allulose, d-psicose) is a rare sugar monosaccharide, the C-3 epimer of fructose, used as a low-energy sweetening ingredient with a technological profile close to sucrose (sweetness, bulking, browning). In formulation it is mainly used to reduce calories and glycaemic impact versus sugar, while preserving useful sensory and processing properties (e.g., bakery).

Definition

Allulose is a defined substance (not a mixture) with formula C₆H₁₂O₆. Practically, it differs from traditional sugars because it is largely absorbed but poorly metabolised, and is excreted mostly intact; this supports a lower energy contribution than conventional carbohydrates. Relative sweetness is typically around ~70% of sucrose, with perceived intensity depending on matrix and concentration.

The difference between psicose and D-psicose is stereochemical and terminological.

• Psicose
  It is a generic term referring to the monosaccharide allulose without specifying its optical configuration.

• D-psicose
  It indicates the D form, which is the naturally occurring form and the one used in food and nutritional applications.

In practice: in food and ingredient contexts, psicose = D-psicose. The distinction is relevant only in stereoisomeric chemistry.

Main uses

Food.
Used as a sweetening ingredient in powders and syrups, especially in “reduced sugar” or “lower calorie” products, with frequent applications in bakery, dairy, ice cream, and beverages. In food technology it can promote browning and caramel-like notes (Maillard/caramelisation-type reactions), so time/temperature control is a key process driver.

Industrial use.
Raw material for sugar-reduction solutions, with attention to purity, contaminant control, process behaviour (browning, hygroscopicity), and batch-to-batch repeatability.

Key constituents

The ingredient consists mainly of allulose. Practical variability between grades is linked to assay/purity, moisture, ash, impurity profile, contaminants (metals), and physical characteristics (particle size for solids; solids content and viscosity for syrups).

Nutritional use note and bioactive compounds

Allulose is used as a sugar alternative to reduce energy and, in multiple contexts, to limit postprandial glucose rise versus conventional sugars. Formulation should account for: non-1:1 sweetness equivalence to sucrose, impact on texture/moisture, and thermal behaviour (browning tendency).

Energy (calories)

Indicative: very low energy contribution; in some markets a factor up to about 0.4 kcal/g is used for labelling and energy calculations. In practice, the applicable value depends on the regulatory framework of the destination market and product category.

Identification data and specifications

Indicative physico-chemical properties

Functional role and practical mechanism of action

The functional role is sweetening with reduced energy versus sucrose and, in many applications, a “sugar-like” technological behaviour (bulking, mouthfeel, browning). Formulation requires tuning of: effective sweetness in the matrix, balance with other sweeteners, and colour control during heating and shelf life.

Formulation compatibility

In powders: manage ambient moisture and compaction (hygroscopicity), through particle size selection and suitable packaging.
In beverages/syrups: consider solubility, viscosity, and stability over time; validate crystallisation risk under real conditions.
In bakery: browning may occur faster than with sucrose; adjust thermal profile and baking time to avoid excessive colour or overly caramelised notes.

Use guidelines

A practical approach is to set sensory targets (sweetness, body, aftertaste) and technological targets (colour, moisture, texture), then optimise in controlled iterations. Across markets, “calories” definition and labelling rules can differ, so regulatory alignment is needed for claims and nutrition declarations.

Quality, grades, and specifications

Supplier qualification is key: assay/purity, impurity profile, contaminant control, and food-safety standards. Adoption of GMP (good manufacturing practice; benefit: reduces variability and contamination) and HACCP (hazard analysis and critical control points; benefit: identifies and controls food-safety risks via critical control points) supports supply-chain robustness and repeatability.

Safety, regulatory, and environment

Safety should be assessed on the finished product considering dose, consumption frequency, and target population. A practical limit is gastrointestinal tolerance: high intakes can cause gas or laxation (osmotic mechanism), especially as a single dose.

Allergen.
Not typically classified as an allergen.

Contraindications.
Use caution in consumers with sensitive gastrointestinal function (e.g., diarrhoea tendency), and in products delivering high per-serving doses; manage via portioning, directions for use, and tolerance evaluation. For vulnerable groups (young children, people with specific conditions), a conservative approach based on finished-product assessment and destination-market regulation is appropriate.

Formulation troubleshooting

Excessive browning during heating.
Action: reduce temperature or time, adjust ratio with other sugars, optimise moisture and pH of the system.

Powder caking.
Action: reduce residual moisture, use barrier packaging, optimise particle size and storage conditions.

Consumer gastrointestinal complaints.
Action: reduce per-serving dose, distribute daily intake, combine with other sweeteners to lower allulose load, add use advisories where appropriate.

Conclusion

Allulose is a rare sugar sweetener with reduced energy contribution and useful sugar-like functionality for sugar-reduction products. Industrial use requires robust quality control (purity/moisture/contaminants), process management (browning), and attention to GI tolerance and market-specific regulatory framing—particularly in the EU where the novel food pathway is a decisive factor.

Mini-glossary

Epimer. A sugar differing in configuration at a single stereogenic centre (for allulose: C-3 epimer of fructose).
GMP. Good manufacturing practice; benefit: reduces variability and contamination through controlled manufacturing practices.
HACCP. Hazard analysis and critical control points; benefit: systematic prevention and control of food-safety hazards via critical control points.

References__________________________________________________________________________

Daniel H, Hauner H, Hornef M, Clavel T. Allulose in human diet: the knowns and the unknowns. Br J Nutr. 2022 Jul 28;128(2):172-178. doi: 10.1017/S0007114521003172. 

Abstract. D-Allulose, also referred to as psicose, is a C3-epimer of D-fructose used as a sugar substitute in low energy products. It can be formed naturally during processing of food and drinks containing sucrose and fructose or is prepared by chemical synthesis or via enzymatic treatment with epimerases from fructose. Estimated intakes via Western style diets including sweetened beverages are below 500 mg per d but, when used as a sugar replacement, intake may reach 10 to 30 g per d depending on the food consumed. Due to its structural similarity with fructose, allulose uses the same transport and distribution pathways. But in contrast to fructose, the human genome does not encode for enzymes that are able to metabolise allulose leading to an almost complete renal excretion of the absorbed dose and near-to-zero energetic yield. However, in vitro studies have shown that certain bacteria such as Klebsiella pneumonia are able to utilise allulose as a substrate. This finding has been a subject of concern, since Klebsiella pneumoniae represents an opportunistic human pathogen. It therefore raised the question of whether a high dietary intake of allulose may cause an undesirable growth advantage for potentially harmful bacteria at mucosal sites such as the intestine or at systemic sites following invasive infection. In this brief review, we discuss the current state of science on these issues and define the research needs to better understand the fate of allulose and its metabolic and microbiological effects when ingested as a sugar substitute.

Tani Y, Tokuda M, Nishimoto N, Yokoi H, Izumori K. Allulose for the attenuation of postprandial blood glucose levels in healthy humans: A systematic review and meta-analysis. PLoS One. 2023 Apr 6;18(4):e0281150. doi: 10.1371/journal.pone.0281150.

Abstract. D-Allulose is a rare sugar that exists in nature. It is a food ingredient with nearly zero calories (<0.4 kcal/g) and has many physiological functionalities such as attenuation of postprandial blood glucose levels, attenuation of postprandial fat mass accumulation, and anti-aging property. This study focused on the postprandial blood glucose changes in healthy humans by a systematic review and meta-analysis. They were chosen because of its importance to a prevention from diabetes. The study objective was to examine acute blood glucose concentrations of healthy humans after the meal with and without allulose. The study collected all D-allulose related studies from various databases. A forest plot of the comparison between an allulose intake group and the control group showed both 5g and 10g intake groups have the significantly smaller area under the curve of postprandial blood glucose levels. It means that D-Allulose attenuates postprandial blood glucose concentrations in healthy humans. As the result, D-Allulose is a valuable blood glucose management tool for healthy humans and diabetes patients. Allulose Diet enables reduction of sucrose intake through Sugar Reformulation in the future diet. Copyright: © 2023 Yuma et al.

Xia Y, Cheng Q, Mu W, Hu X, Sun Z, Qiu Y, Liu X, Wang Z. Research Advances of d-allulose: An Overview of Physiological Functions, Enzymatic Biotransformation Technologies, and Production Processes. Foods. 2021 Sep 15;10(9):2186. doi: 10.3390/foods10092186. 

Abstract, d-allulose has a significant application value as a sugar substitute, not only as a food ingredient and dietary supplement, but also with various physiological functions, such as improving insulin resistance, anti-obesity, and regulating glucolipid metabolism. Over the decades, the physiological functions of d-allulose and the corresponding mechanisms have been studied deeply, and this product has been applied to various foods to enhance food quality and prolong shelf life. In recent years, biotransformation technologies for the production of d-allulose using enzymatic approaches have gained more attention. However, there are few comprehensive reviews on this topic. This review focuses on the recent research advances of d-allulose, including (1) the physiological functions of d-allulose; (2) the major enzyme families used for the biotransformation of d-allulose and their microbial origins; (3) phylogenetic and structural characterization of d-allulose 3-epimerases, and the directed evolution methods for the enzymes; (4) heterologous expression of d-allulose ketose 3-epimerases and biotransformation techniques for d-allulose; and (5) production processes for biotransformation of d-allulose based on the characterized enzymes. Furthermore, the future trends on biosynthesis and applications of d-allulose in food and health industries are discussed and evaluated in this review.

Wang L, Cui Y, Lu Y, Zhao Z. Comprehensive Analysis of Allulose Production: A Review and Update. Foods. 2024 Aug 17;13(16):2572. doi: 10.3390/foods13162572.

Abstract. Advancements in D-allulose production have seen significant strides in recent years, focusing on enzymatic conversion methods. Key developments include traditional immobilization techniques, the discovery of novel enzymes, directed evolution studies, and biosynthesis through metabolic pathway modification. Enzymatic conversion, particularly utilizing D-allulose 3-epimerase, remains fundamental for industrial-scale production. Innovative immobilization strategies, such as functionalized nano-beads and magnetic MOF nanoparticles, have significantly enhanced enzyme stability and reusability. Directed evolution has led to improved enzyme thermostability and catalytic efficiency, while synthetic biology methods, including phosphorylation-driven and thermodynamics-driven pathways, have optimized production processes. High-throughput screening methods have been crucial in identifying and refining enzyme variants for industrial applications. Collectively, these advancements not only enhance production efficiency and cost-effectiveness but also adhere to sustainable and economically viable manufacturing practices. The past five years have witnessed critical developments with significant potential impact on the commercial viability and global demand for allulose.

Zhang W, Chen D, Chen J, Xu W, Chen Q, Wu H, Guang C, Mu W. D-allulose, a versatile rare sugar: recent biotechnological advances and challenges. Crit Rev Food Sci Nutr. 2023;63(22):5661-5679. doi: 10.1080/10408398.2021.2023091. 

Abstract. D-Allulose is the C-3 epimer of D-fructose, and widely regarded as a promising substitute for sucrose. It's an excellent low-calorie sweetener, with 70% sweetness of sucrose, 0.4 kcal/g dietary energy, and special physiological functions. It has been approved as GRAS by the U.S. Food and Drug Administration, and is allowed to be excluded from total and added sugar counts on the food labels. Therefore, D-allulose gradually attracts more public attention. Owing to scarcity in nature, the bioproduction of D-allulose by using ketose 3-epimerase (KEase) has become the research hotspot. Herein, we give a summary of the physicochemical properties, physiological function, applications, and the chemical and biochemical synthesis methods of D-allulose. In addition, the recent progress in the D-allulose bioproduction using KEases, and the possible solutions for existing challenges in the D-allulose industrial production are comprehensively discussed, focusing on the molecular modification, immobilization, food-grade expression, utilizing low-cost biomass as feedstock, overcoming thermodynamic limitation, as well as the downstream separation and purification. Finally, Prospects for further development are also proposed.